Jet propulsion units



Mn ch 4, 1958 M. KADO'ISCH ETAL JET PROPULSION UNITS Filed April 29. 1952 s Sheets-Sheet 2 j ATTORNE/s M. KADOSCH EFAL 2,825,204 PJET PROPULSION UNITS March 4, 1958 Filed April 29, 1952 iNVENTOR 14777 AME/3 tates JET PROPULSION UNITS Application April 29, 1952, Serial No. 284,861

Claims priority, application France May 30, 1951 12 Claims. (Cl. 60 -35.6)

Unite Jet propulsion units are of two types: those in which the motive gas flows in a continuous way (e. g. jet and propeller turbine engines, ram-jet engines) and those in which the motive gas flows in an intermittent Way (e. g. pulse-jet engines, piston-jetengines).

The researches carried out by the applicants on pulsejet units have enabled them to determine that the output of these units could be increased to a very large extent if the jet pipe is operated in such manner that it may readily be filled with air between two gas pulses, the air thus introduced being forced by the following pulse with increase in momentum at constant kinetic energy of its jet. The term jet pipe Will be taken to designate the pipe which leads the exhaust gas to the propelling nozzle of the jet propulsion unit; for instance, in the case of a jet turbine engine, the jet pipe is the pipe connecting the exhaust cone, i. e. the assembly extending at the exhaust end of the annular turbine, with the propelling nozzle.

The applicants have thought of applying this principle of dilution to continuous flow jet units and it is this particular application of the means necessary for initially converting the continuous flow into a pulsating flow which forms the subject of the present invention.

It has already been proposed to dilutethe gases being exhausted from the turbine of a turbo-jet unit before these gases are admitted into the reaction nozzle, but this dilution, which is effected continuously and is not accompanied by any change in the continuous nature of the flow of the gases is very diflerent from that which is proposed in accordance with the invention, according to which the continuous flow of the gases is converted into a pulsating flow thereby allowing atmospheric air to fill the jet pipe in the intervals between the pulses.

The means suitable for converting the continuous flow into a pulsating flow are numerous. It is, for example, possible to subdivide the customary jet pipe into a number of elementary jet pipes disposed in parallel relation and to direct the jet of gas successively towards the said elementary jet pipes, each associated with means for permitting the refilling with air to take place in the intervals between the pulses.

The control of the gas jet for directing it successively towards the various elementary jet pipes may itself be carried out in various ways; it is possible, for example, to use arrangements for deflecting gas jets such as already described by the applicants in their U. S. Patent No. 2,702,986, issued on March 1, 1955, and applications Serial No. 268,016, filed January 24, 1952, now Patent No. 2,738,646, issued on March 20, 1956, Serial No. 221,551, filed April 18, 1951, now Patent No. 2,793,493, issued on May 28, 1957, and Serial No. 221,552, filed April 18, 1951, or even to provide a movable distributor which receives the continuous gas jet and is displaced for sending this jet successively to the jet pipes to be supplied.

The description which follows with reference to the atom: O

2,825,204 Patented Mar. 4, 1958 accompanying drawing, given by way of non-limitative example, will enable it to be better understood how the invention may be carried into effect, the features which become apparent both from the drawing and the description obviously forming part of the said invention.

Fig. 1 is a diagrammatic view in longitudinal'section of a first embodiment of the invention.

Fig. 2 is a transverse section on the line II--II of Fig. 1.

Figs 3 and 4 on the one hand, and Figs. 5 and 6 on the other hand, respectively show two other embodiments as sections similar to those of Figs. 1 and 2, Figs. 4 and 6 being sections through lines IVIV and VIVI of Figs. 3 and 5, respectively.

Fig. 7 is a longitudinal section of a fourth embodiment in which the dilution air is admitted at least in part through orifices opening upstream.

Fig. 8 is a diagrammatic axial section of a fifth embodiment having a rotatable distributor associated with elementary jet pipes.

Fig. 9 is a diagrammatic section on the line IX-IX of Fig. 8.

The duct 1 receives the continuously flowing gases which, in an ordinary jet propulsion unit: turbo-jet unit turbo-prop unit or ram-jet unit, would travel to the propelling nozzle in order to produce the propulsive jet, which would also be continuous.

Fig. 1 shows in a very diagrammatic manner and simply for clarity in the drawing, an example comprising a turbine compressor unit preceding the duct 1 and comprising an air-intake casing 2, a compressor 3, combustion chambers 4 and a gas turbine 5 driving the compressor 3.

In an ordinary reaction jet unit of this type, the duct 1 would directly lead the exhaust gas from the exhaust cone of the turbine to a single jet pipe ending with a propelling nozzle.

In the embodiment of the invention which is illustrated in Figure 1, the duct 1, assumed to be of circular section, leads into a jet pipe assembly having two concentric walls, viz.: an outer wall 6 and an inner wall 7: both the walls are flared, but the inner wall 7 has an inlet opening 8 of the same diameter or preferably of a slightly larger diameter than the duct 1, so that when the deflector device about to be described is not operating, the exhaust gas may flow without any obstruction through the central jet pipe defined by the inner wall 7. Furthermore, the external wall 6 is of such dimensions that the annular outlet orifice 6a between the latter and the wall 7 has a cross-section equal to that of the outlet orifice 7a of the wall 7.

The arrangement thus comprises a central jet pipe and an annular peripheral jet pipe which will be respectively referred to by the numbers 7a and 6a of the outlet orifice.

The deflecting arrangement comprises a tapered member 9 of small dimensions disposed on the axis of the duct 1 a little forward of the inlet opening 8. This tapered member 9 is hollow and comprises a circular slot 10 extending over its entire periphery, the two halves of the tapered member separated by this slot being connected together in a suitable manner, for example, by means of an internal axial rod 11.

The interior of the tapered member may be supplied with compressed air, taken from a suitable source, for example, an intermediate stage of the compressor 3, by means of a pipe 12 equipped with a rotating cock. This cock may be formed very simply by a cylindrical member 14 enclosing a diametrical partition 15 driven con tinuously about the spindle 16 of the cylinder by means of a suitable motor M. It will be seen that in the position of the partition 15 as shown in Figure 1, the supply p 3 of air to the member 9 is shut off, while in a position turned through 90", the air is admitted to the member 9.

The slot 10 is disposed in such manner that the circular jet of air which leaves it has a velocitycomponent which is directed crosswise of the axial flow of the gases in the duct 1, as shownby theari'ow f in the top half of Figiife'l.

With the partition ineinber 1'5 ihth'e position shown in Figure l,the slot10 is not supplied with air, the gas flowing through the duct not being deflected, it enters the central jet pipe 7a. This is indicated by the arrows parallel to the axis, which'are shown in the lower half of Figure l.

V In the 90 position of the, partition member 15, the slot 10 is supplied with air and'the jet which le'avesthis slot deflects the gas jet flowing in the duct '1. The gas jet will adhere to the roundedportiontib of the wall 6, this being the portion which merges into the wall "of the duct 1. The gas jet thuspasses into the annular jet pipe 6a. It is this jet which is shown by the arrows indicated in the top half of Figure l. A grid of annular vanes 17 positioned at the start of the annularpipe between 6 and 7 evens the flow of the gas jet in the said pipe.

The continuously flowing gas in the duct 1 thus flows sometimes through the central jet pipe 7a and sometimes through the annular jet pipe 6a.

There is thus produced a pulsating jet in each of these etpipes.

If the annular jet pipe 6a is considered, for example, in the interval between successive pulses of gases delivered to this jet pipe, the said nozzle is filled with at mospheric air passing at the rearthrough the outlet orifice and drawn in by the depression which follows each pulse. .This air ,is driven out by'the following pulse of gases, which acts on this air as would a piston. There is then obtained an increase in the momentum and consequently of the propulsive thrust with constant kinetic energy.

, Thesameremark applies forthe central jet pipe 7a whieh is filled with air between two successive pulses in this jet pipe. 7

In order to avoid a portionof the jet leaving .the' annular jet pipe being drawn back into the central jet-pipe under the action of thesuction exerted by the flow of gas at the point where it passes from the duct 1 into the annularet pipe, there may be provided, for filling this jet pipe w th air between two pulses, pipes 18 disposed radially in the annular jet pipe and providing communication between thelatmosphere and this jet pipe at points distributed on the wall 7.

In order that the increase in thrust resulting from the increase in the momentum may be used to -the best advantage, it is recommended that both the central jet pipe and the annular jet pipe be given a divergent'form, at least at the start of these jet pipes. In this manner, the increase in thrust is transmitted to the jet pipes themselves and the How of the gases in the jet unitupstream of the jet pipes is not disturbed. This is shown in the drawing. It has already been pointed out that the outlet areas of the two jet pipes, i. e. the areas of the propelling nozzles are preferably equal; it is also expedient thatthe laws in accordance with which the sections vary in the two et pipes between the inlet openings and the outlet openings or propelling nozzles should be the same, in order that the two pulsating jets leaving the two nozzles have equal or substantially equal velocities and produce similar propulsive etfects, but this is not absolutely essential.

In the modification shown in Figures 3 and 4, the two jet pipes 6a and 7a through whichlthe jet passes alternately are juxtaposed instead of being coaxial as in the. case of Figures 1 and 2. The duct 1 supplying the gas 18 assumed to be of rectangular cross-section, as are also the jet pipes 6a-7a which are separated from one an other by the streamlined partition 20. The blast nozzles Illa-10b of the auxiliary deflecting jet. are formed on two opposed walls of the duct 1, parallel to the partition 20. They are supplied with air alternately by means of a rotary cock 14, 15, which is similar to that which has been described with reference to Figures 1 and 2 but which diflers therefrom in that it is a two-way cock. It follows that when the slot 10a is supplied (the case shown in Figure 3), the gas jet is deflected towards the jet pipe 6a, while the jet pipe 7a isfilled with atmospheric air, this filling being assisted by the depression left by the preceding pulse. Conversely, when the slot 10b is supplied, the jet is deflected towards the jet pipe 70', while the jet pipe 6a is filled with air. The effect obtained is the same as that described in the preceding embodiment. Vanes 21 may be provided at the inlet to the two jet pipes in order to even the flow.

The modification shown in Figures 5 and 6 differs from the previous embodiments merely by the substitution of solid baflles for the fluid bat-fies created by auxiliary gas jets. The solid bafiles are formed by two small bars 22a, 22b disposed perpendicular to the axis of the duct 1, which is assumed to be of rectangular section, and along two opposed walls of the said duct. The small bars are driven in continuous rotation about their longitudinal axis 23a, 23b by a mechanism which may comprise an auxiliary motor of any desired type, such as an electric motor, air motor or the like. They are arranged, as shown in the drawing, so that at the moment when one of the bars 22a, for example, is disposed with its sur' face perpendicular to the direction of flow of the gases in the duct, 1, the surface of the other is parallel to the said direction.

The bars thus deflect the gas jet alternately towards the jet pipes 6a and 7a arranged as above. It is advisable to provide at least" one vane 24a, 24b located downstream of each of the bars'and serving to cause the deflected stream to adhere to the curved wall at the end of each jet pipe.

Other varies for evening the flow may be providedas at 21' in Figures?) and 4.

"It is obviously possible to haveothermovablesolid baffle devices for obtaining the deflectionof the gases towards one jet pipe and then towards the otherso as thereby to obtain a pulsating flow in each of the jetpipes, which are refilled with air in the intervals between the pulses.

In the foregoing examples, the airis admitted into the jet pipes in the intervals between the pulses through the ejection orifices or propelling nozzles. It is also possible to efiect the admission of the air through forwardly facing orifices whereby the ram effect of inflowing air is utilized for refilling the jet pipes when flying at high s eed.

Figure 7 shows one embodimentof this type which is similar to that of Figure 1, but which differs therefrom by the presence of annular orifice 25 facing upstream and communicating with the peripheral jet pipe 6a. This orifice thus renders it possible for the air of the relative wind to travel directly to the said jet pipe 6a inthe intervals between the pulsation.

For the purpose of filling the internal jet pipe 6bwith air, it is also possible to provide an air-collecting ring '26 and to connect it to the interior of this jet pipe by a number of pipes 27 disposed in radial planes.

The upper half of Figure 7 shows an example in which the circular slot 10 is fed with auxiliary air under pres sure and deflects the gas jet towards the peripheral jet pipe 6a, while the lower half of the same figure shows the case in which, when. air is not being supplied to the slot 10, the jet passes directly into the central jet pipe 6b.

The arrangements described above operate as a whole as intermittent switching arrangements.

It is also possible to provide continuous rotatable switching arrangements.

In Figures 8 and 9, the gases leaving the duct 1 pass into the distributor 28 which is in the form of a section of a tube mounted in such manner as to be capable of turning about the axis of the duct 1. This tube 28 may carry, for example, a stub shaft 29 located in alignment with the axis of the duct 1 and mounted in a fixed bearing 30.

The tube 28 is curved in such manner that when it rotates, its outlet opening 28a is displaced in front of the inlet openings of a number of jet pipes 6a, 6b, 6c disposed in ring formation.

Consequently, as the tube 28 rotates continuously about the axis of the duct 1, it directs the gas jet successively towards the different jet pipes, thereby generating a pulsating flow in each of them, while in the intervals between the pulses, the jetpipes are refilled with air entering freely into their inlet openings.

The rotation of the tube 28 may be produced by a suitable motor, for example, an electric motor 31 driving the shaft 29. I

It may also be carried out automatically under the action of the flow of the gases. For this purpose, it is sufficient to bend the tube 28 in such manner that as the gases leave the said tube, they have a tangential velocity component (a component which, in the position of the tube 28 as shown in Figure 8, would pass through the centre of the orifice 28a and would be perpendicular to the plane of the figure).

It is obvious that other forms of rotatable switching arrangements may be provided.

What we claim is:

1. A jet propulsion unit comprising, in succession from the front to the rear of the unit, a combustion apparatus adapted to generate a continuous flow of motive gas, a duct to which said gas is continuously supplied, two rearwardly-directed jet pipes having each an inlet opening communicating with said duct, said pipes extending gen-' erally parallel with each other and with said duct, and intermittently operating means arranged in said duct in the vicinity of one of said inlet openings for intermittently deflecting the motive gas flow towards the other inlet opening and into the corresponding pipe, said intermittently operating deflecting means comprising nozzle means adapted to form a screen-like fluid jet crosswise of the motive gas flow through said duct, piping means for supplying fluid under pressure to said nozzle means, and valve means for intermittently cutting off the flow of said fluid through said piping means.

2. A jet propulsion unit comprising, in succession from the front to the rear of the unit, a combustion apparatus adapted to generate a continuous flow of motive gas, a

duct to which said gas is continuously supplied, at least two rearwardly-extending divergent jet pipes having each a permanently open inlet adjacent said duct and facing towards the front of the unit and an outlet opening to the atmosphere and facing towards the rear of said unit to form a propulsive jet producing forward thrust, the axes of said jet pipes being rectilinear and parallel to the general axis of the unit, and means associated with said duct in the vicinity of said inlets for urging the motive gas flow successively towards one inlet and then the other and into the respective pipes, whereby the gas flows intermittently through each pipe.

3. A propulsion unit according to claim 1, wherein the nozzle means is located substantially in the axis of said duct.

4. A propulsion unit according to claim 1, wherein the nozzle means is located substantially on the periphery of said duct.

5. A propulsion unit according to claim 2, wherein the intermittently operating deflecting means comprises a solid obstacle movable successively to an operative position and to an inoperative position.

6. A jet propulsion unit comprising, in succession from the front to the rear of the unit, a combustion apparatus adapted to generate a continuous flow of motive gas, a duct to which said gas is continuously supplied, two rearwardly-directed, generally coaxial jet pipes, one inside the other, having each an inlet opening communicating with said duct, said pipes extending generally parallel with said duct, and intermittently operating means arranged in said duct in the vicinity of the inlet opening of the inner pipe and in general coaxial relation therewith for intermittently deflecting the motive gas'flow towards the inlet opening of the outer pipe.

7. A propulsion unit according to claim 6, wherein the ductis generally coaxial with the two pipes and has a diverging shape in its part communicating with the inlet openings of said pipes, and the area of the inlet opening of the inner pipe is at least equal to that of the smallest cross-section of said diverging part of said duct.

8. A propulsion unit according to claim 6, wherein the intermittently operating deflecting means comprises nozzle means mounted on a streamlined support located substantially in the axis of said duct, said nozzle means being adapted to form a screen-like fluid jet crosswise of the motive gas flow through said duct, piping means for supplying fluid under pressure to' said nozzle means, and valve means for intermittently cutting off the flow of said fluid through said piping means.

9. A propulsion unit according to claim 6, further comprising duct means opening at one end to the atmosphere and at the other end to an intermediate part of the inner pipe downstream of the inlet opening thereof, for the introduction of atmospheric air into said inner pipe.

10. A propulsion unit according to claim 6, further comprising duct means opening at one end to the atmosphere and at the other end to the outer pipe, for the introduction of atmospheric air into said outer pipe.

11. A propulsion unit according to claim 2 wherein the means for urging the motive gas flow successively towards the inlets of the pipes comprises a movable tube having an end in permanent communication with the duct and another end adapted to register successively with said inlets.

12. A propulsion unit according to claim 11 comprising a multiplicity of rearwardly-extending jet pipes arranged in annular formation and uniformly distributed about the axis of said unit, the inlets of said pipes lying in a plane perpendicular to said axis and the movable tube being rotatable about said axis.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Aug. 28, 

